Notices of Tornadoes, Sj'c. 81 



for a continual discharge of electricity from those above, and that 

 the difference between an ordinary thunder storm and one ac- 

 companied by a tornado, consists in the presence of a conductor 

 of clouds, which seem to maintain the combat between the up- 

 per portion of the tornado and the ground beneath. At Chatenay 

 this conductor was formed by the influence of an upper thunder 

 cloud, which forced the lower portion of an inferior thunder cloud 

 to descend and come into contact with the terrestrial surface." 



Peltier concurs with me in the opinion that the tornado super- 

 sedes lightning by affording a conducting communication between 

 the terrestrial surface and thunder cloud : but he conceives that 

 the cloud by its descent becomes the conductor through which 

 the electric discharge is accomplished : whereas agreeably to the 

 explanation which I suggested, a vertical blast of air and every 

 body carried aloft contributes to form the means of communication. 

 Agreeably to this suggestion the electric fluid does not pass by 

 conduction, but "convection," as explained in my letter of the 

 26th ult. That the idea of the Parisian savant that the cloud 

 acts as a conductor is untenable, must be evident, since the light 

 matter of which a cloud is constituted could not be stationary be- 

 tween the earth and sky in opposition to that upward aerial cur- 

 rent of which the violence is proved to be sufficient to elevate 

 not only water, but other bodies specifically much heavier than 

 this liquid. 



So much of the narrative of Peltier as relates to the repulsion 

 between the thunder clouds, is inconsistent with any other facts 

 on record respecting tornadoes which have come within njy 

 knowledge. It should be recollected that this part of the story 

 does not depend upon the observation of the author, and may be 

 due to the imagination of the witnesses whom he examined. 

 The most important part of his evidence is that respecting the 

 effect upon the trees, which appears to me to demonstrate that 

 they were the medium of a tremendous electrical current. 



In my memoir I noticed the injury done to the leaves of trees, 

 and stated my conviction that " as it was i?ico?iceivable that me- 

 chanical laceration could have thus extended itself equally among 

 the foliage, a surmise may he warranted that the change loas 

 effected by electricity associated loith the tornado. ^^ 



Vol. XXXVIII, No. l.—Oct,-Dec. 1839. 11 



